In recent years, in the electronic device manufacture field represented by the manufacture of integrated circuit devices, a demand for high integration of devices is increasing, and therefore, a photolithography technology for forming a fine pattern is considered to be necessary. For that reason, the development of a photoresist composition adaptive with photolithography using, as exposure light, radiations having a wavelength of not more than 220 nm, for example, an ArF excimer laser (wavelength: 193 nm), an F2 excimer laser (wavelength: 157 nm), etc. is desired, and there have been proposed a number of photoresist compositions of a chemical amplification type composed of an acid dissociable functional group-containing polymer compound and a compound capable of generating an acid upon irradiation with radiations (hereinafter referred to as “exposure”) (the latter compound will be hereinafter referred to as “photo acid generator”). For example, there are known photoresist compositions containing, as a component, a polymer compound having an adamantyl group-containing acrylic ester as a constitutional unit as the acid dissociable functional group-containing polymer compound (see Non-Patent Document 1 and Patent Document 1); and photoresist compositions containing, as a component, a polymer compound having a lactone ring-containing constitutional unit as the acid dissociable functional group-containing polymer compound (see Patent Document 2).    Non-Patent Document 1: Journal of Photopolymer Science and Technology, Vol. 9, No. 3, 475 to 487 (1996)    Patent Document 1: JP-A-9-73173    Patent Document 2: JP-A-2004-46206